Rotary-table press with removable punches

ABSTRACT

The invention relates to a rotary press with anti-rotation secured shafts and exchangeable punches attached thereto. The rotary press comprises a punch turn which is universally ensured with the use of anti-rotation secured punch shafts, meaning, not only with rotation-symmetrical but also with roll-guided punches, is solved in such a way that the exchangeable punch is executed in a rotational manner, where a circumferential recess in the stem of the punch is envisaged, into which a component such as a spring thrust piece engages for the purpose of fixation, and that the shell surface of the exchangeable punch indicates a zone which interacts with a zone of the external component, either force-locking or positive locking, in such a way that the punch receives a turning movement at a defined point of the pitch circle of the punch circumference.

DESCRIPTION

The invention concerns a rotary press with exchangeable punches.

The known rotary presses for pressing tablets in particular essentiallyconsist of a rotor with a die table, an upper and lower part, where theupper part and the lower part contain and guide the upper and lowerpunches engaging in the dies of the die table.

Rotary presses with devices for turning the punches and rotary presseswith anti-rotation secured shafts and exchangeable punches attachedthereto are known (Technical Rotary Presses of Messrs Korsch PressenAG/Series TRP 700, which have been on the market since approximately1995 (information release of Korsch Pressen GmbH for customers,representatives and staff members, Edition No. 1, March 1995)).

In the DE-GM 88 16 064 a rotary press is described where the upper andlower punches have rotational movement around their longitudinal axisdirectly after passing the press rolls acting on them. The rotation ofthe upper and lower punches around their longitudinal axis is effectedeither by means of a frictional connection of the upper and lowerpunches with acting press rolls arranged directly behind the upper andlower punches, with spring force against the upper and lower punchesforward-pressable guide curve sections or by means of an interaction ofa serration with a stationary located spur rack arranged at the punchshaft.

By means of the rotational movement of the upper and lower punchesdirectly after the pressing operation and during the withdrawal of theupper and lower punches from the die of the die table, a separation ofthe upper surface of the pressed tablet from the upper punch should beachieved as a minimum. Where particularly adhesive materials to bepressed are concerned, a rotational movement of the lower punch is alsoto avoid the adhesion between this and the underneath side of thetablet.

A disadvantage in the frictional connection between the upper and lowerpunches and the related guide curve sections is, however, the fact thatwear of the material occurs in this case and, on the other hand, nodefined rotation of the upper and lower punches is carried out.Subsequently, with a varying strength of rotation of the upper and lowerpunches, the pressed form body can even be destroyed in the process. Adisadvantage with the serration arranged at the punch shaft is, on theone hand, the fact that specially designed upper and lower punches mustbe used and, on the other hand, that a friction between the serrationsof upper and lower punches and the relevant, stationary arranged spurrack occurs because the serration of the upper and lower punches ismoved together with these in the axis direction of the upper and lowerpunches.

In the GB-A-155 594, a rotary press is described which is provided withdevices for turning the punches, on whose turn-actuated punch shaftsexchangeable punches are envisaged.

A particular disadvantage is the fact that this proposed solution cannotbe adopted for punch shafts whose head form does not allow a rotation ofthe punch (roll-guided punches) and/or heads whose microsection surfacerequires that the heads have to be moved right through in a certainorientation below the press roll (heavy-duty punch).

The invention is based on the task assignment of developing acategory-related rotary press where and with which the adhesive effectof the tablet on the upper and lower punches is securely avoided bymeans of the generation of turn-off forces on the surface of the tablet,in particular where a punch turn is universally ensured with the use ofanti-rotation secured punch shafts, meaning, not only withrotation-symmetrical but also with roll-guided punches.

According to the present invention, a rotary press with anti-rotationsecured shafts and exchangeable punches attached thereto arecharacterised in such a way that the exchangeable punch, opposite itspunch shaft in each case, is rotational in design, where acircumferential recess in the trunnion stem of the punch exists, intowhich a connecting component, in particular a spring thrust piece,engages for the rotational connection of the punch with the punch shaft,and that the shell surface of the exchangeable punch indicates a zonewhich interacts with a zone of a component arranged location-fixed atthe rotary press opposite the punch circumference, in a force-locking orpositive locking manner in such a way that the punch receives arotational movement at a defined point of the pitch circle of the punchcircumference.

The external component for the upper punch and the lower punch isradially and elastically bearing-supported as a punch rotating deviceaccording to a most preferred embodiment of the invention and executedin such a way that the engagement at the upper and lower punch isseparately adjustable and can be brought to differently defined pointsof the pitch circle, where the external component is radially positionalaround the pitch circle of the punch circumference.

The preferential execution of the engagement zone of the shell surfaceof the punch as a separate element allows higher life service and aneconomical replacement of parts/components subject to wear.

Furthermore and as a result of convenient exchangeability of thisseparate element, it is possible to adapt production quickly andeconomically to material-specific features of various press materials,for example when changing over from one product to another.

With a change of the serration, for example, the angular rotation of thepunch can be changed, meaning, the path of rotation performed by thepunch is extended or shortened. In addition, it is relativelyuncomplicated to change over from a positive locking to a force lockingconnection.

With the invention, rotary presses with rotational and exchangeablepunches can be executed for rotation-symmetrical and for roll-guidedpunches.

According to an alternative embodiment of the invention and instead ofthe punch, the dies are trunnion-mounted and have a serration orfriction surface on their outer sides.

The invention will be better understood by an example of an embodiment,as shown in a drawing, of an upper and lower punch of a rotary press.The drawings illustrate the following items:

FIG. 1: a schematic vertical cross-section through an upper and lowerpunch in the working position with the upper and lower punch protrudingfrom the die;

FIG. 2: the arrangement according to FIG. 1 in the position with theupper and lower punch inserted into the die, including the externalcomponent;

FIG. 3 a: a side view (partially cross-sectioned) onto detail Iaccording to FIG. 2, and

FIG. 3 b: a top view of detail I from FIG. 2.

In FIG. 1 a part of a known rotary press is shown in a schematicillustration, consisting of an arrangement of rotor upper part 11, dietable 13 with die 14 and rotor lower part 12. The upper punch shaft 15and the lower punch shaft 16 run in guide bushes 17, 18, which arelocated in the rotor upper part 11 and in the rotor lower part,respectively, and are anti- rotation secured with fitting pieces 19, 20.The guide bushes 17, 18 have fitting key grooves 21, 22, in whichfitting keys 23, 24 of the upper and lower punch shafts 15, 16 arearranged. In this way, the punch shafts 15, 16 are also anti-rotationsecured with reference to the rotor 11, 12 and the press roll (notshown), respectively.

A seal ring 25 is arranged in the upper guide bush 17 in order toprevent the penetration of dirt and to avoid lubrication oil losses. Thelower shaft guide 18 is protected with a bellows 10.

The normally exchangeable but solidly located punches according to thestate of the art are, in accordance with the present invention, executedas exchangeable and rotational upper punches 6 and lower punches 7.

This is achieved by means of a circumferential recess 27, 30 in the stem8, 9 of the upper and lower punch 6, 7. Into this recess 27, 30, acomponent engages, for example a spring thrust piece 4, for the purposeof positional fixation. In order to additionally secure this fixation ofthe rotational punch 6, 7 in the direction of movement, a pin 5 engagesinto the recess 27, 30.

For the purpose of achieving a positive locking between the rotationalpunch 6, 7 and an external turning device, a mounted element 1 with anouter serration is arranged on a recessed area of the rotational punch6, 7. The lock-in carrying effect between this element 1 and therotational punches 6, 7 is ensured by means of a fitting key 2. Theouter serration can be directly applied to the punch 6, 7. The separateapplication of the outer serration onto a separately mounted element 1has the advantage that it is possible to eliminate wear economically byreplacing the mounted element 1, meaning, the entire punch 6, 7 does nothave to be replaced.

In FIG. 2, the arrangement of a rotary press is shown where a punch head32 with guide rolls 31 is envisaged. This embodiment requires ananti-rotation secured shaft 15, 16 of the upper and lower punch 6, 7corresponding to the FIG. 1.

In the FIG. 2 there is, furthermore, an external component is shown onthe periphery of the pitch circle of the punch circumference which isused as a punch turning device 33.

The punch turning device 33 is mounted near the non-illustrated pressroll on a dust ring 34 and is moveable with a skid 35 concentrically tothe pitch circle in the press roll zone. As a result, the engaging pointof the serration elements 29 (FIG. 2) of the punch turning device 33with the mounted element 1 with outer serration (FIG. 1) can be adjustedin such a way that the most advantageous point with a sufficientlyminimised pressing force, which is just being exerted by the press roll,is set. By way of a threaded rod 28 which is connected to the skid 35,the engaging points of the fixed-located serration elements 29 areindividually adjustable in the height to the rotational punch 6, 7. Thisis necessary in order to be able to react to changed insertion depths ofthe punches 6, 7.

The fixed-located serration elements 29 are horizontally moveable aroundthe threaded rod 28, acting as a vertical axis, with height-adjustablebearing bushes 26. The horizontal movement is restricted to a zone of afew millimeters by means of an elastic and/or spring element 3. By meansof a light pressure, set with the elastic and/or spring element 3, ontothe rotational punch 6, 7 a carrying torque with a simultaneous evadingpossibility of the system is produced.

A defined turning movement and, subsequently, a high-precision andsynchronous run-in of the serration of the mounted element 1 and of thefixed-located serration elements 29 is not ensured in every case. Forthis reason, this evading possibility is necessary for a secure andreliable operation.

The high accelerating forces occurring during the impact of the mountedelement 1, moving with the circumferential speed of the punches 6, 7,with the outer serration and the fixed- located serration elements 29can lead to destruction of the serrations at a very early stage. Inorder to avoid major impact forces of an impulsive nature, the outerserration of the mounted element 1 and the fixed-located serrationelements 29 are low-mass in design and executed very elastically asyielding serration elements in according with the illustration in FIG.3.

In FIG. 3 a, in a schematic side view, and in FIG. 3 b in a top view, anembodiment of the serration element 29 and the outer serration of themounted element 1 is shown, where the fixed-located serration element 29is executed in a comb-type design with spring elements as prongs 37.Numerous prongs 37 of the serration element 29 ensure that one prong 37succeeds in establishing an engagement (meshing) with the outerserration of the mounted element 1, in which case the outer serration ofthe mounted element 1 indicates a purposeful tooth form such as a sawtooth form, trapezoidal tooth form.

The joint between the fixed-located punch shaft 15, 16 and therotational punch 6, 7 is sealed off by means of a seal 36, such as alabyrinth seal, to protect against material dust and fouling matter ofthe bearing locations.

As a punch turning device 33 a tangential friction wheel or similar,acting on the punch 6,7, for the purpose of establishing force-lockingengagement is also conceivable.

A non-illustrated alternative embodiment of the invention envisagesthat, instead of the punch 6, 7, the dies 14 are located in trunnionsupports, and that these dies have on their outer sides a serration or afriction surface.

And with such a solution also, forces can be produced on the uppersurface of the tablets which prevent a sticking of the tablet on theupper and/or lower punch.

REFERENCE NUMBERS LIST

-   1. Element with outer serration-   2. Fitting key-   3. Spring element-   4. Component, spring thrust element-   5. Pin-   6. Upper punch-   7. Lower punch-   8. Punch stem-   9. Punch stem-   10. Bellows-   11. Rotor upper part-   12. Rotor lower part-   13. Die table-   14. Die-   15. Upper punch shaft-   16. Lower punch shaft-   17. Guide bush-   18. Guide bush-   19. Fitting piece-   20. Fitting piece-   21. Fitting key groove-   22. Fitting key groove-   23. Fitting key-   24. Fitting key-   25. Seal ring-   26. Bearing bush-   27. Recess-   28. Threaded rod-   29. Serration element-   30. Recess-   31. Guide roll-   32. Punch head-   33. External component (punch turning device)-   34. Dust ring-   35. Skid-   36. Seal-   37. Spring element (prongs)

1. Rotary press comprising a plurality of punches arrayed in a circlefor rotating about the rotary press, each of said punches being anexchangeable punch disposed rotatably about a punch shaft, the punchshaft being secured against rotation with respect to its longitudinalaxis, a connecting component residing in a circumferential recess of astem of the punch effecting a rotational connection of the punch withthe punch shaft, an external component residing substantially externallyof the circle, a second zone of the external component residing adjacentthe circle, a shell surface of the punch comprising a first zone whichis engageable with the second zone of the external component, the secondzone being fixed with respect to the rotation of the punches about thecircle, the first zone and second zone together comprising a means foreffecting a force-locking or a positive locking in such a way that thepunch receives a turning movement at a defined point of circle. 2.Rotary press according to claim 1, wherein the shell surface of thepunch comprises the first zone for interacting with the second zone ofthe external component.
 3. Rotary press according to claim 1, whereinthe external component is separately adjustable and moveable intodifferent, defined points of the circle, the external component beingradially positionable around the circle.
 4. Rotary press according toclaim 1, wherein the external component has a bearing location which isradially elastic.
 5. Rotary press according to claim 1, wherein a sealseals a joint between the punch shaft and the punch.
 6. Rotary pressaccording to claim 1, wherein the first zone of the shell surface of thepunch interacts with the second zone of the external component is aseparated and exchangeable element of the punch.
 7. Rotary pressaccording to claim 1, wherein the first and second zones of the shellsurface and the external component, respectively, comprise serration orfriction surfaces.
 8. Rotary press according to claim 7, wherein theserration or friction surfaces are low in mass and elastic in acircumferential direction.
 9. Rotary press according to claim 8, whereinthe second zone of the external component is an elastically yieldingspring element disposed in a movement direction of the punch, such thatthe elastically yielding spring element can simultaneously absorb anoccurring impact energy and, ensure a secure and reliable engagementinto the first zone of the shell surface of the punch.
 10. Rotary pressaccording to claim 8, wherein the first zone of the shell surface of thepunch comprises a tooth profile adapted to the second zone of theexternal component.
 11. Rotary press according to claim 8, wherein thesecond zone of the external component comprises at least two springelements situated one behind the other in movement direction of thepunch and arranged in a comb-like manner.
 12. Rotary press comprising aplurality of dies and a plurality of punches arrayed in a circle forrotating about the rotary press, each of said punches being anexchangeable punch attached to a punch shaft, the punch shaft beingsecured against rotation with respect to its longitudinal axis, anexternal component residing substantially externally of the circle, asecond zone of the external component residing adjacent the circle, thedies being trunnion-supported and comprise on their outer sides a firstzone which is engageable with the second zone of the external component,the second zone being fixed with respect to the rotation of the punchesabout the circle, the first zone and the second zone together comprisinga means for effecting a force-locking or positive locking, in such a waythat the dies receive a rotational movement at a defined point ofcircle.
 13. Rotary press according to claim 1, wherein the connectingcomponent is a spring thrust piece.
 14. Rotary press according to claim5, wherein the seal is a labyrinth seal.
 15. Rotary press according toclaim 10, wherein the tooth profile is a trapezoidal or a saw toothprofile.